The present invention relates to an ejector for drawing a fluid to be removed by using a negative pressure.
An ejector of the present art typically has a chamber provided with a fluid intake opening through which a fluid is drawn under suction, and a nozzle for directing a jet of fluid towards an outlet opening of the chamber. When the jet entrains a fluid in the chamber and expels it via the outlet opening, a negative pressure is created in the chamber.
FIG. 1 shows such an ejector. As shown, the ejector includes an ejector body 10 having a suction chamber 1. The ejector body has a jet nozzle portion 2, a tubular fluid inlet portion 3 and a tubular fluid outlet portion or diffuser portion 4. The nozzle portion 2 is connected to a drive fluid introduction pipe 5 which is in turn connected to a high pressure drive fluid source (not shown). In operation, drive fluid Q1 in jet form is discharged into the suction chamber 1 from the nozzle portion 2 towards the diffuser portion 4. The jet of the drive fluid Q1 moves out of the suction chamber 1 through the diffuser portion 4, thereby creating a negative pressure in the suction chamber 1; as a result, fluid Q2 is drawn into the suction chamber 1 through the tubular fluid inlet portion 3 and, then, discharged from the suction chamber 1 through the diffuser portion 4.
One drawback of this arrangement is the likelihood that solid material present in the form of fumes or mist in an entrained fluid Q2 will be deposit on surfaces of suction chamber 1, diffuser portion 4 and/or nozzle portion 2. Such deposition of material, particularly if it occurs on the surface of an inlet passage portion 6 of diffuser portion 4, will substantially reduce suction capability of the ejector.
This deposition problem is also liable to occur when a solid material is created by reaction of a material in fluid Q2 with drive fluid Q1. For example, in the case that the fluid Q2 is a gas containing boron trichloride (BCl3) which is strongly reacts with water, and fluid Q1 is air containing moisture, a reaction between boron trichloride in fluid Q2 and moisture in fluid Q will produce hydrochloric acid (HCl) in gas form and boric oxide (B2O3) in solid form. Consequently, boric oxide thus produced is liable to adheres to the interior surfaces of the ejector. Similarly, when fluid Q2 contains a material such as silicon tetrachloride (SiCl4) or titanium tetrachloride (TiCl4) which are strongly reactive with water, a solid material will be formed by reaction.
In such conventional ejectors, therefore, it has been necessary to periodically disassemble and clean the ejector, thus preventing operation in the apparatus in which it is housed. To overcome this problem, it has been proposed that an ejector be provided with a water cleaning mechanism, whereby it can be cleaned of solid deposits without the need for disassembly. While such a water cleaning mechanism avoids the problems of disassembly, when using it to clean an ejector housed in an assembly, operation of the assembly must still be halted.
The present invention has been made with a view to overcoming these problems.
In accordance with the present invention, there is provided an ejector which is characterized by being provided with an interior surface wetting device. The interior surface wetting device comprises a cleaning liquid inlet opening to be fluidly connected to a source of a cleaning liquid, and a cleaning liquid outlet opening for introducing the cleaning liquid into a suction chamber of the ejector in such a way as to form a thin wall of the cleaning liquid over an interior surface of the suction chamber and/or an interior surface of the fluid outlet of the ejector. The interior surface wetting device may include a cleaning liquid introduction pipe which is provided in place of or in addition to the cleaning liquid inlet and outlet openings stated above to introduce the cleaning liquid into the suction chamber in such a way as to form a thin wall of the cleaning liquid over the interior surface of the ejector.
By forming a thin wall of cleaning liquid on the interior surface of the ejector, deposition of solid material thereon can be prevented. Incidentally, cleaning liquid may be any kind of liquid such as water and chemical solution which functions to prevent deposition of solid material.
The above and other objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments when taken in conjunction with the accompanying drawings.